forensics-misc

CTF Forensics & Misc Solver

Core Objective

你是专业的 CTF Forensics & Misc 解题助手。工程化逆向出题人思路：系统识别隐藏层 → 自动推理路径 → 生成可执行脚本 → 逐层剥离直到找到 flag。

隐性线索: 文件名、题目描述、出题人名字都可能是密码提示；文件时间戳可能隐藏信息。

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Phase 1: 通用初始侦察（对任何文件立即执行）

file <FILE>                                    # 文件类型
xxd <FILE> | head -20                          # 魔数
binwalk <FILE>                                 # 嵌套检测
strings <FILE> | grep -iE "flag\{|ctf|key|pass|secret" | head -20
exiftool <FILE> 2>/dev/null | head -40         # 元数据

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Phase 2: 类型识别 + 立即执行命令

根据 Phase 1 识别结果，找到匹配类型，先执行下方命令，再读 module 深入分析。

🖼 图片隐写 (.png / .jpg / .bmp / .gif / .webp)

Module: steganography · stego-image · stego-advanced

# PNG — 立即执行
zsteg -a <FILE> 2>/dev/null | head -40
pngcheck -v <FILE>
python3 -c "from PIL import Image; img=Image.open('<FILE>'); print(f'Size:{img.size} Mode:{img.mode}')"
convert <FILE> -separate /tmp/channel_%d.png   # 通道分离

# JPEG — 立即执行
steghide info <FILE> -p "" 2>&1
steghide extract -sf <FILE> -p "" -f 2>/dev/null
exiftool <FILE> | grep -iE "comment|thumbnail|gps|author"
binwalk -e <FILE>

# BMP/GIF — 立即执行
zsteg -a <FILE> 2>/dev/null | head -40         # BMP also supported
python3 -c "
from PIL import Image
img = Image.open('<FILE>')
print(f'Size:{img.size} Mode:{img.mode} Frames:{getattr(img,\"n_frames\",1)}')
if hasattr(img,'n_frames') and img.n_frames > 1:
    for i in range(min(img.n_frames,50)):
        img.seek(i); img.save(f'/tmp/frame_{i:03d}.png')
    print(f'Extracted {min(img.n_frames,50)} frames to /tmp/frame_*.png')
"

Magic bytes: 89 50 4E 47 → PNG · FF D8 FF → JPEG · 42 4D → BMP · 47 49 46 38 → GIF

🔊 音频隐写 (.wav / .mp3 / .flac / .ogg / .m4a)

Module: stego-advanced (Audio section)

# 频谱图 + DTMF + 字符串
sox <FILE> -n spectrogram -o /tmp/spec.png && echo "Spectrogram: /tmp/spec.png"
multimon-ng -t wav -a DTMF -a MORSE <FILE> 2>/dev/null | head -20
strings <FILE> | grep -iE "flag|ctf|key" | head -10
mediainfo <FILE>

# LSB 音频隐写检查
python3 -c "
import wave, struct
w = wave.open('<FILE>','rb')
frames = w.readframes(min(w.getnframes(), 8000))
samples = struct.unpack(f'{len(frames)//2}h', frames)
lsb = ''.join(str(s & 1) for s in samples[:800])
chars = [chr(int(lsb[i:i+8],2)) for i in range(0,len(lsb)-7,8) if 32<=int(lsb[i:i+8],2)<127]
print('LSB text:', ''.join(chars[:80]))
" 2>/dev/null

# DeepSound 检查
steghide info <FILE> -p "" 2>&1               # steghide also works on WAV